1. Technical Field
The present invention relates generally to a joined structure of dissimilar metallic materials having different characteristics. More specifically, the invention relates to a joined structure of a current-carrying contact or arching contact which are used for, e.g., a power breaker, or a coating end structure of a metal base and a coating material for improving conductivity and heat resistance.
2. Description of the Prior Art
Conventionally, the friction welding or diffusion joining is carried out to join rod-like or tubular dissimilar metallic materials. Referring to FIG. 1, an example of joining of dissimilar metallic materials using the friction welding will be described. As shown in FIG. 1A, metallic materials 1 and 2 having different material characteristics, e.g., aluminum or an aluminum alloy and copper or a copper alloy, are clamped by a chuck of a pressure welding device. Then, one is rotated, and portions to be joined are heated by frictional energy to be upset-pressed by an axial welding pressure P to be joined to each other. As shown in FIG. 1B, the metallic materials 1 and 2 are joined to each other, so that the quantities and shapes of burrs 5 of the joined metallic materials 1 and 2 on the longitudinal sections are different from each other in accordance with the respective material strengths. Furthermore, in FIGS. 1A and 1B, 3 denotes a fixed shaft of the chuck of the friction welding device, and 4 is a rotating shaft thereof. In conventional joining of joints, there is a problem in that the reliability of the joined portion is low since the impact strength of the joined members is small. This tendency is the same as that in a joined structure of dissimilar materials using a joining method which uses any one of the cold welding, hot welding, diffusion joining, explosion welding, forge welding, ultrasonic joining, brazing, soldering, resistance welding and adhesive in addition to the above described friction welding.
Therefore, in conventional friction welding for dissimilar materials, the diameter of one of materials, which has a greater thermal expansion coefficient, is set to be greater than that of the other material to relieve residual stress generating on the joined interface to improve the joining strength (Japanese Patent Laid-Open No. 6-47570). In the hot welding of an aluminum material to a copper material, the convex copper material is allowed to butt the aluminum material at an included angle of 15 to 45 degrees to be joined thereto by the current-carrying heating to improve tensile strength (Japanese Patent Laid-Open No. 4-143085). In the joining of a ceramic to a metal, a ceramic forming angle of a part of a peripheral portion of a joined interface of a ceramic member to the surface of a body to be joined is set to be smaller than or equal to 80 degrees or greater than or equal to 100 degrees to relieve thermal stress (Japanese Patent Laid-Open No. 1-282166). In the joining of members having different thermal expansion coefficients, an edge portion of a joined interface of a member having a small thermal expansion coefficient is formed so as to have a curved surface having a greater radius than a predetermined value viewed from the joined interface, to relieve thermal stress (Japanese Patent Laid-Open No. 1-282167).
It is an object of the above described conventional methods to relieve residual stress and thermal stress and improve tensile strength, but it is not an object thereof to enhance the impact strength of the joined member and to enhance the reliability of the joined portion.
As described above, in the joining of dissimilar materials having different material characteristics, there is no problem as shown in FIGS. 2 and 3 with respect to static joint strength by optimizing the joining conditions. That is, the tensile strength of a joined member of dissimilar metals is not different between the central portion and the end portion of the joined surface. However, as shown in FIGS. 4 and 5, it is clear that the impact strength remarkably decreases at the end portion of the joined surface so that the impact strength of the whole joint is low. Therefore, there is a problem in that the impact strength of the joined member is low.
On the other hand, a coating material is coated on a metal base by the thermal spraying, PVD, CVD or the like to improve conductivity and heat resistance. When a metal base has a rigidity different from that of a coating material, e.g., when a coating material having a smaller rigidity than that of a metal base is coated on the metal base or when a coating material having a greater rigidity than that of a metal base is coated on the metal base, there is a problem in that the impact strength of the coated member comprising the metal base and the coating material is low to decrease reliability.
This tendency is the same as that in a coating structure obtained by any methods, such as welding, brazing, soldering and adhesive, in addition to the coating methods, such as thermal spraying, PVD and CVD.
It is therefore an object of the present invention to provide a joined structure which enhances the impact strength of a joined member and which has a high reliability, in the joining of dissimilar metallic materials having different material characteristics.
It is another object of the present invention to improve the impact strength of a coating member, which comprises a metal base and a coating material having a different material characteristic from that of the metal base, to provide a coating structure having a high reliability.
In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, one of which is joined to the other metallic material having a smaller rigidity than that of the one of metallic materials, wherein an angle of the one of metallic materials to a free edge of the one of metallic materials at an end portion of a joined surface between the metallic materials is greater than or equal to 120 degrees or in the range of from 55 degrees to 85 degrees.
According to another aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, which comprises a contact portion of a current-carrying contact for use in a power breaker, the contact portion being made of copper or a copper alloy, and a remaining portion of the current-carrying contact other than the contact portion, the remaining portion being made of aluminum or an aluminum alloy, and wherein an angle of the contact portion of copper or the copper alloy to a free edge of the contact portion at an end portion of a joined surface between the contact portion and the remaining portion is greater than or equal to 120 degrees or in the range of from 55 degrees to 85 degrees.
According to another aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, which comprises a contact portion of an arcing contact for use in a power breaker, the contact portion being made of a copper-tungsten alloy, and a remaining portion of the arcing contact other than the contact portion, the remaining portion being made of a material selected from the group consisting of iron, an iron alloy and a copper alloy, and wherein an angle of the contact portion of copper-tungsten alloy to a free edge of the contact portion at an end portion of a joined surface between the contact portion and the remaining portion is greater than or equal to 120 degrees or in the range of from 55 degrees to 85 degrees.
According to another aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, one of which is joined to the other metallic material having a smaller rigidity than that of the one of metallic materials, wherein when both of angles of the one of metallic materials and the other metallic material to free edges of the respective metallic materials at an end portion of a joined surface between the metallic materials are smaller than 90 degrees.
According to another aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, one of which is joined to the other metallic material having a smaller rigidity than that of the one of metallic materials, wherein when one of angles of the one of metallic materials and the other metallic material to free edges of the respective metallic materials at an end portion of a joined surface between the metallic materials is 90 degrees, the other of the angles of the one of metallic materials and the other metallic material to the free edges of the respective metallic materials at the end portion of the joined surface is smaller than 90 degrees.
According to another aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, one of which is made of aluminum or an aluminum alloy and the other of which is made of copper or a copper alloy, the metallic materials being joined by the friction welding, wherein an angle of the other metallic material to a free edge of the other metallic material at an end portion of a joined surface is set to be in the range of from 50 degrees to 85 degrees.
According to another aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, one of which is made of aluminum or an aluminum alloy and the other of which is made of copper or a copper alloy, the metallic materials being joined by the friction welding, wherein an angle of the other metallic material to a free edge of the other metallic material at an end portion of a joined surface is set to be greater than or equal to 120 degrees.
According to another aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, one of which is made of aluminum or an aluminum alloy and the other of which is made of copper or a copper alloy, the metallic materials being joined by the friction welding, wherein angles of the metallic materials to a free edge of the other metallic material at an end portion of a joined surface are set to be smaller than 90 degrees.
According to another aspect of the present invention, there is provided a joined structure of dissimilar metallic materials, one of which is made of aluminum or an aluminum alloy and the other of which is made of copper or a copper alloy, the metallic materials being joined by the friction welding, wherein when one of angles of the metallic materials to free edges of the respective metallic materials at an end portion of a joined surface is 90 degrees, the other angle of the metallic materials to free edges of the respective metallic materials at the end portion of the joined surface is set to be smaller than 90 degrees.
According to another aspect of the present invention, there is provided a coating end structure comprising: a recessed metal base; and a coating member of a coating material which has a smaller rigidity than that of the metal base and which is coated on the metal base, wherein an angle of the metal base to a free edge at the coating end portion is greater than or equal to 120 degrees or in the range of from 55 degrees to 85 degrees.
According to another aspect of the present invention, there is provided a coating end structure comprising: a recessed metal base; and a coating member of a coating material which has a greater rigidity than that of the metal base and which is coated on the metal base, wherein an angle of the metal base to a free edge at the coating end portion is smaller than or equal to 60 degrees or in the range of from 95 degrees to 125 degrees.
According to another aspect of the present invention, there is provided a coating end structure of a current-carrying part for use in a power breaker having a coating structure comprising a recessed contact body and a contact portion coated on the contact body, wherein the contact body is made of a metal base, and the coating portion is made of a coating material having a smaller rigidity than that of the metal base, and wherein an angle of the metal base to a free edge at the coating end portion is smaller than or equal to 60 degrees or in the range of from 95 degrees to 125 degrees.
According to another aspect of the present invention, there is provided a coating end structure of a conductor for use in a power breaker or switch having a coating structure comprising a recessed conductor body and a conductor contact portion coated on the conductor body, wherein the conductor body is made of a metal base, and the conductor contact portion is made of a coating base having a greater rigidity than that of the metal base, and wherein an angle of the metal base to a free edge at the coating end portion is smaller than or equal to 60 degrees or in the range of from 95 degrees to 125 degrees.
According to a further aspect of the present invention, there is provided a coating end structure of a moving blade or a combustor for use in a gas turbine having a coating structure comprising a recessed body and a corrosion resisting portion coated on the body, wherein the body is made of a base metal, and the corrosion resisting portion is a coating material having a smaller rigidity than that of the metal base, and wherein an angle of the metal base to a free edge at the coating end portion is greater than or equal to 120 degrees or in the range of from 55 degrees to 85 degrees.
According to a still further aspect of the present invention, there is provided a coating end structure of a moving blade or a combustor for use in a gas turbine having a coating structure comprising a recessed body and a corrosion resisting portion coated on the body, wherein the body is made of a base metal, and the corrosion resisting portion comprises a bond coat material and a topcoat material which have a smaller rigidity than that of the metal base, and wherein an angle of the metal base to a free edge at the coating end portion is greater than or equal to 120 degrees or in the range of from 55 degrees to 85 degrees.
According to the present invention, it is possible to provide a joined structure having a high impact strength and a high reliability by setting an angle of dissimilar metallic materials having different rigidities to a free edge at the end portion of the joined surface to a specific range or by setting an angle of a copper alloy to a free edge at the end portion of the joined surface so as to decrease stress concentration at the joined portion in a joined structure of an aluminum alloy and the copper alloy which are friction welded to each other.
According to the present invention, it is also possible to provide a coating end structure having a high impact strength and a high reliability by setting an angle of a metal base to a free edge at the coating end portion of a coating member, which comprises the metal base and a coating material having a smaller rigidity than that of the metal base, to a specific range.